This is your brain on hate

Researchers at University College London, using fMRI scanners, have identified …

The advent of non-invasive imaging devices have been a real boon to neuroscientists in their quest to understand how the brain works. A new study, conducted by researchers at University College London and published in PLoS ONE, has now identified the regions in the brain that are activated when people experience the emotion of hate, and the combination of these regions is distinct to that emotion alone.

The study involved fMRI scans of 17 individuals. Prior to the imaging, each volunteer had identified an individual whom they hated, predominantly a former lover or a coworker, although in one case it was a politician. They provided the researchers with an facial image of the object of their hate, along with a gender-matched neutral figure. These were edited and presented in a greyscale format along with blank greyscale images while the subjects were undergoing an fMRI scan.

The acquired data was then analyzed to compare the pattern of brain activation recorded when the subject was viewing a face to baseline brain activity; neutral faces were then compared to hated faces. Interestingly, there were specific areas of the brain that registered activity when confronted by a hated face that weren't seen with neutral faces, namely the right putamen, both sides of the premotor cortex and medial insula, and the frontal pole.

There was also a linear relationship between the intensity of hatred (as measured by a survey) and activity at some of these regions, as well as a few additional ones (the right insula, right premotor cortex, and right fronto-medial gyrus). The superior frontal gyrus also showed decreased activation when challenged with hated faces compared to neutral faces.

Areas of the brain that might be thought to be involved in hate, such as those that are known to be activated by related emotions such as fear or anger (the amygdala, the hippocampus, or the anterior cingulate) were not involved in the hate response. The involvement of the frontal cortex regions and the putamen is intriguing, as these are involved with motor planning. The authors speculate that this could be due to the brain preparing to attack or defend itself against the hated individual.

There was a little commonality with a prior study by the same group, which focused on the brain activation patterns seen with the emotion love. According to Professor Semir Zeki, "Significantly, the putamen and insula are also both activated by romantic love. This is not surprising. The putamen could also be involved in the preparation of aggressive acts in a romantic context, as in situations when a rival presents a danger."

"A marked difference in the cortical pattern produced by these two sentiments of love and hate is that, whereas with love, large parts of the cerebral cortex associated with judgment and reasoning become de-activated, with hate only a small zone, located in the frontal cortex, becomes de-activated. This may seem surprising since hate can also be an all-consuming passion, just like love. But whereas in romantic love, the lover is often less critical and judgmental regarding the loved person, it is more likely that in the context of hate, the hater may want to exercise judgment in calculating moves to harm, injure or otherwise extract revenge."

This last bit might have important implications for criminal proceedings regarding premeditation and crimes of passion.

The authors plan to continue this study to see if different types of hate, such as those that extend towards entire groups, show the same pattern of brain activity as that focused on a specific individual.